This invention relates to glazing panels, and in particular to chromogenic glazing panels and to a process for manufacturing such glazing panels.
Although the invention is described herein with particular reference to suspended particles devices (SPDs) it will be understood that it has applications to other chromogenic glazing panels and to other glazing panels, for example electrochromic glazing panels and vacuum insulating glazings. Glazing panels according to the invention may have various applications: they may be used as architectural products, for example they may be incorporated in windows, in double or multiple glazing units and in doors; or as products for the automotive industry, for example as rear-view mirrors, sunroofs or automotive windows.
Chromogenic technologies may offer a dynamic control over the opto-energetic characteristics of a glazing. Chromogenic technologies include electrochromic devices (ECDs), reflective hydrides, liquid crystals, suspended particle devices (SPDs), photochromics and thermotropics. Electrochromic and suspended particle devices undergo a reversible change in optical properties upon application of an electrical voltage, photochromic materials darken under the direct action of sunlight and thermotropic (or thermochromic) materials respond to heat. Liquid crystals windows switch quickly from a transparent state to a diffuse white state and reflective hydrides switch to a reflective state. Glazing panels which can in this way dynamically control light transmission are also called “smart windows”.
Suspended particle devices are conventionally made using two sheets of glass, spaced apart from each other and sealed together along their edges, the glass sheets being coated with a conductive layer on their surface facing the space between them. The space between the two glass sheets is filled with a functional material which may be a liquid, a gel or a resin comprising suspended particles. The suspended particles may be comprised in a film sandwiched between the glass sheets. When an electrical voltage is applied to the conductive layers, a change in the luminous transmission of the glazing panel is observed. In electrochromic devices, the functional material between the two glass sheets generally comprises an electrochromic electrode, a counter-electrode and between both electrodes, an ion conductor. The ion conductor may be a liquid, a gel, a polymer or a ceramic conductor.
To obtain a good quality SPD wherein the suspended particles are comprised in a liquid, a gel or a resin, it is necessary that the space between the two sheets of glass be as constant as possible. However, the larger the glazing panel, the more the space between the two glass sheets may vary in an uncontrollable manner due to deformation of the glass sheets. For the same reason, i.e. the resistance to deformation of the glass sheets, the thickness of the glass sheets has an influence on the constancy of the space between the two sheets of glass. Furthermore, when filling the space between the two sheets of glass with a functional material comprising suspended particles, this material has a tendency of pushing the two glass sheets away from each other, thereby also providing unacceptable differences in the distance between the two sheets of glass, at different portions of the glazing panel.